Google has changed the way it's counting devices running particular Android versions. "Beginning in April, 2013, these charts are now built using data collected from each device when the user visits the Google Play Store. Previously, the data was collected when the device simply checked-in to Google servers. We believe the new data more accurately reflects those users who are most engaged in the Android and Google Play ecosystem." The change does actually make sense - reflecting the kind of usage developers are interested in - but the fact that this also makes Jelly Bean jump from 16% to 25% surely played an important role here too. This means that Ice Cream Sandwich and later now account for about 54% of Android devices in use.

Keep in mind that with two year contracts there are a lot of people that have a gingerbread phone that are not "novice" users. 4.0 was a big change and most phones with 2.3 will not be upgraded due mainly to the size of the partitions on the phone. I bought my wife get the Samsung stratosphere(basically an slightly upgraded Galaxy S) because it the best phone available on Verizon with a Keyboard. Apps need to support older version, and often it's not really that hard with Android. Especially if it's a simple app that doesn't need the newer APIs.